World and Olympic 100m champion Justin Gatlin could escape a lifetime ban if he testifies against his coach, the US Anti-Doping Agency has said.

The American, 24, is facing a life ban following a second positive drugs test.

But Usada said that ban could be reduced to eight years if Gatlin provided information in its case against his coach Trevor Graham.

Usada and athletics' governing body are investigating Graham, several of whose athletes have received drugs bans.

Graham denies direct knowledge or involvement in drugs use. He said Gatlin was "spiked" by a massage therapist who rubbed testosterone cream on his legs without his knowledge.

If an athlete can provide information on individuals involved in doping conspiracies we would always welcome that evidence

Travis TygartUsada general counsel

Gatlin, who denies knowingly using performance-enhancing drugs, tested positive for testosterone at a meeting in Kansas in April.

He is planning to mount a defence when his case is heard by Usada, which is expected to be next week.

Usada general counsel Travis Tygart was quoted by the AP news agency saying that, by testifying against Graham, Gatlin would activate the "substantial assistance" provision in the World Anti-Doping Agency's code.

That can reduce a ban by proving an athlete "bears no significant fault or negligence".

"If an athlete can provide information on individuals involved in doping conspiracies and can help us catch distributors or users of these drugs, we would always welcome that evidence," said Tygart, who would not comment on Gatlin or any other specific case.

He added: "Since we don't have any criminal investigative powers - like wiretaps, warrants for searching premises, etc - it takes information coming to us from people aiming for a reduction in their own doping sentences," Tygart said.

"It's one way we can continue to actively pursue those involved in doping practices."